textproduct: Albany

WHAT HAS CHANGED

Forecast update this morning based on radar trends to decrease PoPs across much of the area for the rest of this morning. Showers and thunderstorms will then develop this afternoon. Activity looks most numerous north of I-90, with more scattered coverage from around I-90 south. SPC has maintained a Marginal Risk (level 1 of 5) of severe thunderstorms for this afternoon into early this evening.

KEY MESSAGES

1) Scattered showers and thunderstorms develop across eastern NY and western New England today. There is a marginal risk (level 1 of 5) for isolated severe thunderstorms, mainly this afternoon, with damaging winds, frequent lightning and heavy downpours the primary hazards.

2) Isolated to scattered showers and thunderstorms are expected Monday and Tuesday, especially near and north of I-90.

3) Chances of showers and thunderstorms return late next week as temperatures trend warmer.

DISCUSSION

KEY MESSAGE 1...

Latest water vapor imagery shows our parent trough centered just north of the Great Lakes with a secondary shortwave rounding the base through the Ohio Valley. An area of rain and thunderstorms continues to push through PA early this morning ahead of the occluded boundary within a region of diffluent flow downstream of the trough. However, high res and deterministic guidance is in good agreement showing these showers/storms continuing to weaken as they advance north and eastward through sunrise as they outrun the best forcing for ascent. While a few isolated showers develop ahead of the occluded front before sunrise, the weakening area of showers/embedded storms should reach eastern NY and western New England 09 - 15 UTC this morning. The occluded boundary essentially stalls over eastern NY today with the secondary shortwave from the Ohio Valley continuing to rotate into the Northeast, reaching eastern NY by early afternoon. As stronger height falls arrive, expecting scattered clusters of showers/storms to redevelop and track from west to east. Forecast soundings and moisture profiles also show dry air surges into eastern NY/western New England this afternoon as this stronger shortwave arrives. This will help steepen mid- level lapse rates over 6C/km with DCAPE values also rising over 1000 J/kg. The incoming dry air should also help morning stratus break for sun with dew points in the mid to upper 60s supporting sfc-based instability increasing towards 1000 - 1500 J/kg per the REFS and CAMs. Given the incoming closed low, 0-6km shear impressively reaches 40-50kts and 0-3km shear 25-30kts.

Despite these favorable ingredients for severe weather, clouds look to break for sun just as the stronger height falls arrive, limiting the time for the atmosphere to destabilize before convective initiates. In addition, low-level forcing is limited to a weakening warm front lifting northward along a washout occluded front. These help explain why the HREF and REFS both only show low probabilities for updraft helicity values exceeding 20m/s mainly 20 - 00 UTC. This indicates that even as isolated to scattered storm clusters initiate mid to late afternoon into the early evening hours, there should only be isolated instances of severe thunderstorms. Given weak updraft growth, there are also questions if any storms can tap into the stronger shear aloft. This matches with SPC's marginal risk (level 1 of 5) in their Day 1 Convective Outlook. Damaging winds remain the primary hazard from any severe storms that form but any storm can also produce frequent lightning as forecast soundings show sufficient instability extending into the favored -10C to -30C region likely due to the cool/dry air tracking in aloft. Storms can also produce heavy downpours given PWATs over 1". Convection dissipates by 0 - 02 UTC with clouds clearing quickly thereafter, supporting radiational fog overnight where heavy rain fell.

KEY MESSAGE 2...

Our mature closed low slowly propagates into southern Quebec by Monday with its cool pool extending into eastern NY and western New England. Southwest flow aloft will maintain elevated dew points in the mid 50s to low 60s with the 500hPa -15C to -18C cool pool aloft supporting steeper mid-level lapse rates 6 - 6.5C/km with morning sun contributing to SB-CAPE values reaching 500 - 1000 J/kg. As a stronger shortwave rotates around the base of the closed low late Monday morning into the afternoon, stronger forcing for ascent should support a more organized area of rain and even embedded thunderstorms tracking west to east. Given the cool pool, storms will not need to become too tall before lightning develops with any taller updrafts capable of small hail. However, forecast soundings shows low EL heights indicating low-topped convection and thus limiting severe weather potential.

Winds shift westerly by Monday evening in the wake of the shortwave with cool air advection over the still warm lakes supporting a lake effect and upslope rain response. Therefore, we continue to show likely and categorical POPs in the western Adirondacks with chance POPs in the southern Greens and Mohawk Valley. Westerly flow and the trough axis/cool pool under our very slow moving closed low should maintain at least scattered showers during the day on Tuesday favored near and north of I-90. The western Adirondacks and southern Greens will likely receive the highest rainfall amounts. Instability wanes by Tuesday so any storms should be isolated.

KEY MESSAGE 3...

High pressure builds back overhead by Wednesday supporting pleasant and dry conditions. However, the dry break does not last long as yet another shortwave trough approaches the Northeast Thursday into Friday. Southwest flow ahead of it will allow humidity levels to rise once again with temperatures trending slightly above normal. Heights fall in response to the approaching trough and eventual cold front looks to support increased chances for showers and thunderstorms both days. However, there remains uncertainties in timing and coverage of shower/storms as there are discrepancies on the strengthen of the incoming cold front and placement of the parent trough in southern Canada.

AVIATION /13Z SUNDAY THROUGH THURSDAY/

Through 12z Monday...MVFR conditions prevail across all terminals this morning as an initial batch of showers begins to spread into the area. Brief lowering to IFR conditions could result with these showers mainly at KPSF, though upstream obs and forecast soundings don't allude anything past a lower MVFR ceiling and visibility at other sites. TEMPO groups have been added for the next couple of hours to accommodate these anticipated conditions.

A break in precipitation comes in a couple of hours before additional scattered convection is expected this afternoon. While it is still difficult to pin down exactly where and when showers and thunderstorms will occur, latest guidance was fairly consistent with the previously issued PROB30 groups. Therefore, maintained the greatest probability of showers and thunderstorms between 21-01z. ALB may have some lingering showers from 16-19z, but confidence is low in this aspect of the forecast. Additionally, we maintained low MVFR conditions with thunderstorms in the aforementioned PROB30s to convey uncertainty not just in the timing and location, but limited confidence in obtaining IFR conditions.

Once showers and thunderstorms conclude this evening, a swift return to VFR will occur with rapid improvements to visibility and ceiling height. By late this evening/early tomorrow morning, skies should clear, leading to potential fog formation at all sites by the end of the period. Winds will prevail out of the southeast to start the period this morning, with sustained speeds below 10 kt. Winds will pick up a bit by this afternoon to around 10 kt before shifting to the southwest to northwest this evening. Winds overnight will then be light to calm.

Outlook...

Monday Night: No Operational Impact. NO SIG WX. Tuesday: Low Operational Impact. Breezy. Slight Chance of SHRA. Tuesday Night: No Operational Impact. NO SIG WX. Wednesday: No Operational Impact. NO SIG WX. Wednesday Night: No Operational Impact. NO SIG WX. Thursday: Moderate Operational Impact. Breezy. Chance of SHRA...TSRA. Thursday Night: High Operational Impact. Likely SHRA...TSRA. Friday: Moderate Operational Impact. Chance of SHRA...TSRA.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...None. MA...None. VT...None.